One mole of a gas having $\gamma=\frac{7}{5}$ is mixed with one mole of a gas having $\gamma=\frac{4}{3}$. The value of $\gamma$ for the mixture is ( $\gamma$ is the ratio of the specific heats of the gas)

A Carnot heat engine has an efficiency of $10 \%$. If the same engine is worked backward to obtain a refrigerator, then the coefficient of performance of the refrigerator is

The rms velocity of a gas molecules oí mass $m$ at a given temperature is proportional to

The speed of a wave on a string is $150 \mathrm{~ms}^{-1}$ when the tension is 120 N . The percentage increase in the tension in order to raise the wave speed by $20 \%$ is